多线程与单线程比较-蒲公英云

给一个多行的txt文本文件，统计里面每个单词出现多少次（如下图）

单线程代码：

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.TreeMap;
public class TestDemo {
    public static void main(String[] args) {
        FileReader fr = null;
        BufferedReader br = null;
        TreeMap<String, Integer> worldMap = new TreeMap<String, Integer>();
        long start = System.currentTimeMillis();
        try {
            fr = new FileReader("fos.txt");
            br = new BufferedReader(fr);
            String temp = "";
            int num = 0;//读取行数
            while ((temp = br.readLine()) != null) {
                num++;
                String[] splitStr = temp.trim().split(" ");
                for (int i = 0; i < splitStr.length; i++) {
                    if (worldMap.containsKey(splitStr[i])) {//原Map中包含key
                        Integer count = worldMap.get(splitStr[i]) + 1;
                        worldMap.put(splitStr[i], count);
                    } else {
                        //原map中不包含这个key（单词）
                        worldMap.put(splitStr[i], 1);
//                        System.out.println("不包含");
                    }
                }
            }
            System.out.println("读取文件总行数：" + num);
            for (String key : worldMap.keySet()) {
                Integer wordNum = worldMap.get(key);
                System.out.println(key + "出现的次数为：" + wordNum);
            }
            long totalTime = System.currentTimeMillis() - start;
            System.out.println("程序运行时间：" + totalTime);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                br.close();
                fr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

运行结果：

多线程代码：

import java.util.HashMap;
import java.util.Map;
public class wordCount implements Runnable {
    String content = "";
    Map<String, Integer> map = new HashMap<>();
    public wordCount(String content) {
        this.content = content;
    }
    @Override
    public void run() {
        String[] split = content.trim().split(" ");
        for (int i = 0; i < split.length; i++) {
            if (map.containsKey(split[i])){
                Integer value = map.get(split[i]) + 1;
                map.put(split[i],value);
            }else {
                map.put(split[i],1);
            }
        }
    }
}
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class wordCountTest {
    static Map<String, Map<String, Integer>> threadMAP = new HashMap<>();
    public static void main(String[] args) {
        long start = System.currentTimeMillis();
        FileReader fr = null;
        BufferedReader bf = null;
        int lineNum = 0;
        ExecutorService executorService = Executors.newCachedThreadPool();
        try {
            fr = new FileReader("fos.txt");
            bf = new BufferedReader(fr);
            StringBuffer listStrBuf = new StringBuffer("");
            String lineStr = "";
//            boolean tag = true;
            while ((lineStr = bf.readLine()) != null) {
                listStrBuf.append(lineStr + " ");
                lineNum++;
                if (lineNum % 100000 == 0) {
                    wordCount wordCount = new wordCount(listStrBuf.toString());
                    listStrBuf.delete(0, listStrBuf.length());
                    Thread thread = new Thread(wordCount);
//                    thread.start();
                    executorService.execute(thread);
                    threadMAP.put("thread-" + lineNum / 100000, wordCount.map);
                }
            }
            if (listStrBuf.toString().length() > 0) {
                wordCount wordCount = new wordCount(listStrBuf.toString());
                Thread thread = new Thread(wordCount);
                executorService.execute(thread);
                threadMAP.put("thread-last", wordCount.map);
            }
            System.out.println("文件总行数为：" + lineNum);
            executorService.shutdown();
            while (true) {
                if (executorService.isTerminated()) {
                    Map<String, Integer> mapResult = new HashMap<>();
//                    for (Map<String, Integer> tempMap : threadMAP.values()) {
//                        System.out.println(tempMap.keySet());
//                    }
                    for (String key :           //thread-1  thread-2  .......  thread-last
                            threadMAP.keySet()) {
                        Map<String, Integer> perThreadWorldNum = threadMAP.get(key);
                        Set<String> perThreadWords = perThreadWorldNum.keySet();
                        Iterator<String> iterator = perThreadWords.iterator();
                        while (iterator.hasNext()) {
                            String word = iterator.next();
                            if (mapResult.containsKey(word)) {
                                Integer wordsNum = perThreadWorldNum.get(word);
                                Integer haveNum = mapResult.get(word);
                                mapResult.put(word, wordsNum + haveNum);
                            } else {
                                mapResult.put(word, perThreadWorldNum.get(word));
                            }
                        }
                        /*
                        System.out.println(key);
                        System.out.println(threadMAP.get(key).keySet());
                        for (String word :
                                threadMAP.get(key).keySet()) {
                            System.out.print(word + ":" + threadMAP.get(key).get(word) + " ");
                        }
                        System.out.println();*/
                    }
                    Set<String> resultWords = mapResult.keySet();
                    for (String word : resultWords) {
                        System.out.println(word + " : " + mapResult.get(word));
                    }
                    break;
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                fr.close();
                bf.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        long endTime = System.currentTimeMillis() - start;
        System.out.println("程序运行时长：" + endTime + "ms");
    }